The present invention relates to a loudspeaker, and more particularly to an assembling of a horn loudspeaker, thereby improving sound characteristic.
The horn loudspeaker operates to directly propagate sound waves produced at a diaphragm passing through a horn without diffusion. The sound is compressed to be a high sound pressure. Air in the horn operates as resistance to increase radiation resistance and efficiency. The horn loudspeaker has a feature of a high efficiency of change in sound energy. Thus, the horn loudspeaker is widely used in various fields such as home Hi-Fi system and business PA system.
FIG. 11 shows a conventional horn loudspeaker. A horn loudspeaker 10 has a yoke 20 having a center hole 20b formed in a yoke base 20a, an annular magnet 60 mounted on the yoke base 20a around the center hole 20b, and an annular pole piece 61 having an inner shoulder portion 61a and mounted on the magnet 60. An annular plate 30 having an integral spacer ring 31 is mounted on the pole piece 61 at an upper peripheral portion thereof through the spacer ring 31 and secured to the yoke 20 with screws. A cylindrical throat member 65 made of aluminum and having a tapered through-hole 66 is mounted in the pole piece 61, magnet 60, and center hole 20b of the yoke 20. Thus, a magnetic circuit is formed with these elements.
On the plate 30 is mounted an annular frame 35 which supports a diaphragm 50 around an edge 51 thereof. A phasing plug 70 is mounted on a top portion of the pole piece 61 in front of the diaphragm 50. The phasing plug 70 has a center slit 71 and side slits 72 and disposed in a throat portion 65a of the throat member 65. Thus, sound waves produced at the diaphragm 50 are propagated in the hole 66 to a mouth portion 75 of the throat member 65 through the slits 71 and 72. A back cover 40 is mounted on the periphery of the plate 30 and secured thereto with screws so as to define a back chamber 45 between the plate 30 and the cover 40.
As shown in FIG. 12, a lower edge of the diaphragm 50 is disposed in a magnetic gap G formed between the pole piece 61 and the plate 30 and secured to a voice coil bobbin 52 having a voice coil 54. The voice coil 54 is disposed in magnetic gap G to be moved in the vertical direction in FIG. 12. The edge 51 of the diaphragm 50 is made of insulation material.
In assembling the magnetic circuit, the throat member 65 is inserted in the center hole 20b at the mouth portion 75 and secured thereto with adhesive. The magnet 60 is mounted on the throat member 65 and the pole piece 61 is mounted on the magnet 60 and the shoulder portion 61a is secured to the throat member 65 with adhesive. Then, the phasing plug 70 is mounted on the pole piece 61 and the diaphragm 50 secured to the plate 30 through the frame 35 is mounted on the phasing plug 70 and the pole piece 61. The spacer ring 31 of the plate 30 is engaged with the pole piece 61 and secured thereto.
When the magnet 60 is energized, the elements in the yoke 20 are attracted with each other by the magnetic force of the magnet to be fixed to each other. Thus, magnetic loss is reduced.
However, in such a speaker, if the loudspeaker 10 is dropped, the elements fixed to each other with magnetic force may be deflected with shock and the throat member 65 may be removed from the magnetic circuit.
In order to eliminate the disadvantage, elements are adhered to each other with adhesives. However, since the adhesive is non-magnetic material, the magnetic force is prevented from flowing, causing a circuit efficiency to be deteriorated.
If the elements are secured to each other with screws, the magnetic flux becomes irregular because of metallic screws.